Mower Blade Hardness

[oldballs]

Since I traded my BX (60 in MMM) for a B with a 60 inch MMM, I saved the spare set of BX blades to use on the B. They are identical except for the center hole. I took the blades to a local welding shop, and the owner said "Sure Thing" to drill a new hole to fit the Kubota B2620 deck. Well, he just called me as said those are the hardest mower blades that he has ever worked on. He said that it burned up his 1 1/8 inch bit. He won't charge me for the bit and expressed disappoint in his attempt. He noted that a Machine Shop might be able to do it.

 

[Farmerford]

Oldballs:

Many years ago I was chief engineer in a plant that made OEM blades for Bush Hog, Woods, and many others. We used 1040 or 5160 steel for most blades and heat treated them to 40-44 Rockwell C hardness. You MMM blades are probably thinner than the 1/2 and 5/8" thick blades we made, but I suspect the hardness is about the same.

A few years ago I had occasion to drill 5/8" holes in some Bush Hog blades and used a solid carbide bit. It worked, but was slow. If the welder used a HSS or even a cobalt steel bit, I am not surprised that it burned up.

 

[oldballs]

Thanks, Farmer....If I take the blades to another shop, I'll let them know ahead of time. A 1 1/8 inch solid cobalt bit would probably cost more than the blades are worth, if I was to buy one myself to use on my 50 year old drill press. Cheers, Mike

 

[oldnslo]

Another option would some one with a milling machine and boring head. They could use a carbide boring tool and machine them out. Again may cost more than the blades are worth.